Metallic container sealing apparatus



Jan. 16, 1951 J. F. BARRY 2,538,496

METALLIC CONTAINER sEALTNG APPARATUS Original Filed Jan. 4, 1947 i. a5 a3 5 F/aa l /NVEA/Tof? BV J. EBA/PRY A TTORNE V Patented Jan. 16, 1951 METALLIC CONTAINER SEALING APPARATUS Joseph F. Barry, Summit, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Original application January 4, 1947, Serial No.

720,263. Divided and this application December 22, 1948, Serial N0. 66,790

4 Claims. (Cl. 219-4) This invention relates to methods and', apparatus for sealing metallic receptacles and more particularly to such receptacles employedas containers for pressure sensitive electrical elements,

such as piezoelectric crystal wafers or blanks used in communication systems.

This application is a division of my application Serial No. 720,263, filed January 4, 1947.

The crystal blank is usually enclosed in a protective casing which is either highly evacuated crlled with dry air under controlled pressure so that the frequency range of the crystal blank may be held stable. When the casing is'formed substantially Whollyvof metal, the crystal blank is mounted on two terminals insulatingly sealed in a base portion and the crystal is enclosed in a cover portion which is soldered or brazed to the base portion.

The soldering or brazing operation is generally performed in a furnace or oven in whichthe temperatures and time -of fusion of the solder seal impose deleterious effects on the frequency characteristics of the crystal blank. The heat radiation `encountered withinthe casing during the heat treatment to effect the seal is such that contamination may occur in the crystal blank or on the surface thereof which seriously "affects the frequency characteristics and renders the crystal unstable inthe frequency range for which it is intended. ,l

An object of this invention is to produce'the final sealing of the casing in a controlled atmosphere so that contamination' of the crystal blank is avoided.

Another object of the invention Vis to manually control the sealing of the casing externally of the low pressure housing in which the crystal units are mountedior final processing." y

A further object of the invention is to, facilitate the manufacturing processes of crystaly production at lowfcost and low shrinkage loss;

Another object of the invention istoy expedite the mass production of crystal units by, multiple sealing methodsr in which a group 'of units are processed in succession in a single operation.

These objects are attained in accordance with the features of this invention by theiinal sealing of the casing unit in a preliminary. low vacuum environment to remove moisture and atmosp heric contaminants which are replaced by .a controlled low humidity atmosphere ofsuitable pres.- sure prior to sealing the casing unit.V This is accomplished'fin one Way by mounting the unit in a bell jar, which may be evacuated .to any desired degree, and supplying dry air to the jar for immersing thejcrystal blank in a controlled and predeterminedenvironment whereby injurious gases or vapors are entirely eliminatedja'nd the frequency characteristics of the crystal'remain con'- stant throughout the operating'liffof the unit.

2 The bell jar assembly is also provided with mounting means for the unit casing and an adjustable movable carbon pencil electrode for seal'- ing the pin hole opening "of the casing through which the unit is evacuated and lled with the controlled pressure of dry air.

A feature of this assembly is the sealing of the movable joint of the carbon or resistive pencil structure whereby the sealing of the crystal unit maybe controlled at a point outside of the bell jar by the operator. The; carbon pencil is supported on a standard which may be rotatably and reciprocally moved to manipulate the pencil with respect to a plurality of units under process in the controlled atmosphere of the sealed bell jar. The standard extends through `ja tubular joint in the base of the jar and is coupled to a knob whichV is controlled by the operator. The standard is sealedvfrom entrance of air through the joints by a resilient or yieldable sleeve rigidly clamped to the tubular joint and the 'knob extension on the standard. After the desired vacuum is attained in the bell jar or if a denite pressure of dry airis supplied to the enclosure including the unit casing, a solder coated insert placed over the pin hole opening inthe side of the cover of the casing is contacted by the carbon pencil and heating current fuses the solder coating on the insert to seal the pin hole in"y the casing. 'I'his arrangement permits the seal Ato be effected in a controlled atmosphere so that injurious matter is eliminated from the sealed unit and thereby the constancy of the frequency characteristics may be preserved. Furthermore, this method materially reduces the numberhof rejects in quantity production of crystal units so that the manufacturing costs are reduced. Y M

Another feature of this invention relates to the mounting 'of a plurality of crystal units in a multiple fixture within the bell; jar so that the seal# ing of a group Iof units maybe accomplished ina single cycle operation. This is accomplished by mounting a number of crystal units in arcuate relation in` a holding fixture which is located within theradius of the movable carbon pencil in the bell jar so that thefpn hole sealing operation may be performed succession with eachV cycle of operation of thefgsjealing method.

These. and other features *of the invention .Will be moreclearly understood from the following detailed description when considered with reference to the accompanying drawings, where- Fig. 1 illustrates, in a perspective view,v the final sealing apparatus with a portion of the bell jar broken away to show the internal structure; Fig. 2 is an elevationalvfew, partly in crosssection, showing the details-of the assembly for the nal sealing of the crystal units;

head 44 by a suitable adhesive "thereon by a Wire' 'bindingdel Fig. als-...any .enlarged detailed view; Vinf.crosszfsec tion, of the sealed joints of the movable standard extending into the bell jar;

totheshapeof .the crystal units, isnigidly ailixed tothe metallic plate 33 by screws; rin spaced rela- -tion to the tubular member 4I and the shaft 42.

Fig. 4 illustrates, in enlarged perspective View.v`lv

the holder for the crystal units employdinathe assembly of Fig. 1; and

Fig. 5 is a fragmentary view, in cross-section, to an enlarged scale, of details of thepinhmeseal in the side of the crystal casing.

The invention is shown, in a particular aspect,

as applicable to a piezoelectric gquartz.crystal blank enclosed in an hermetic-:ally sealedy metallic casing having an elongated base portion Il supporting a pair of terminal prongs I3 and .a ..metatl` lic cover portion I1 which is sealed in a vacuum- .tiglht manner in .accordancelvith the disclosure ,Qf theabovementoned application. `A more detaledidescription. of the. completestructureyothe crystal .unit ans. contained. .in .said application'.

.The coverpcrtionof the casing. isVA provided with ra recess I8 in the sidewallhaving. an aperture .or;.pin hole .I9 .which isseald bya metallic insert disc .soldered overthe .pin hole tocompltejthe vassen'lbly of the unit.

Referringwto Figsl andZ of thejdrawing, the final sealing o.the.crysta1 .unitis progducedinl .the apparatusshown thereinih which a' belljar Yutilized.during thes-ealing operation. :The seal- Aing vassembly has a rectangular. metallic' base or plate 3s 4which `is. mounted inelevatediposiltionby ,four-legs' 3.4' seouredat the. corners thereof to form 'a tablas'tructure.which maybe mounted on .a

bench'. for.. convenient. operation of `.the .various `controls uti1izled in performing. thesealing operation in .the .enclosed chamber.

vided` with an.l 4manila-ting layer 3.51 of thick Sheet material .having a. largecentral cut-outportion `liliana amannular .ring 31., for 'examplepf pliable rubber material, which `is seated Within thecut- .outportion of the. layer` 35 and. rigidly attahed The base.' is. pro- "The arcuate xture is merely shown as an exam- '..pleirofrrxncunting for a plurality of crystal units in .gther'chamber for multiple sealing of the units duringone operation. It is, of course, understood that .the `inventionisfnot limited to this xture `since the 4mounting` may be formed of a complete circle with the movable shaft in a central positionat vthe axis .ofithe chamber.

'The oiset-.shaftAZ is provided with a pair of Mmetallicharms 5I which extend in parallel relation .transversely to the shaft at the inner end thereof, the arms being. attached at one end to the Shaft bya screw and supporting a removable carbon pencil152 atthe opposite end. The-pencil is suspended. vfrom the arms and direct-'ed towards" thei crystal units inthe mountingfjig 49 `sotlilit rotatable movements ofi theshaft v42 will Apermit the travel of the carbon-pencil inanarc cinc'iijli ing with the positions ofthe-'pin hole'opening's I9 in the. crystal units; mounted in the fixture.

A sh'ort tube 53 extends through the plate-33t()- form another inlet into the chamberl opposite the vacuum inlet'SQ, the tube being attachedgexterior tothe chamber, toV an air supply line or hose 54'.

A transformer -is mounted below' theS-base plate. 33 for supplying welding current to the seal-v ing fixture,` the output of the transformer being'- connected to apair @conductora-:56 Whichectend tothe` metallic base and the inneredge off the ,layer 35.. The ring 31 formsa contactsealwith .the ground edge or aglass bell vjar, v vllich forms an enclosing chamber. for performing .the sealing operation,` in accordance Withthis invention. .A nozzle 39 extending belowthe ,table enters. an .opening leading intofthe chamberandis soldered .or Welded to the plate 33 with a couplingconnection clamped to thetable and .a supplyhose' .connected tothe coupling forvevacuatinglthe A. metallic tubular member 4I extendsthrough.tbe1plate33 .and is.. rigidly xed in .position...by,.soldebingthe mid-portion ,to ,the plate, the.tub.u1ai.1member. .beingoffset with respect ,to theaxiscfjthechamr chamber enclosed by the be l1 .jar.

bei'.

inner WalLof' the tubular member, as.s.hownn Fig..3. rhe shaft 42 is provided .with an enlarged. head Mat the outer. end and ahandknob' l5,. ,of nsulatnelmaterlal, is rigidly afxedtotheihead All. ...A resilient. sleeve ,member'lt .preferablycf' rubber tubing., extends between. the tubularmem.- .berAl and the head 44 to formailiexiblecoupling joint .between .the .tubular 4member a 4 I and v'the standard assembly, the rubber sleeve being sealed tothe tubular member and rigidlyniixed theretor by. a clamp 41. Ther s leeveuis also sealedto the andi-.rigidly 'heid into aconduit box 51v attached to' tl'tfe'glowerside` ofA the base. Theconductors are connefctedtofa pair of terminals on a connector blocklifrnountd shafdto seal the pinhole opening in the-crystal .5.5. A movable shatter standard .42,.f9r exam- I.ple l.a...meta1lic rod. .extendsthrollsh .thegtuhular member and .is supported .therein by Na .pair of- 4"spaced insulating bushings ,e3 which ensaee'.tbes

unit.

In the nal sealing process or the'crystal -unit a; plurality of units are inountedin the xture49, With the pinhole openings. I9 uppermostin the mounting, and positioned in the slots 50 so that the terminalV prongs I3 extend'outwardly from the mounting. In this position the pin hole opening is aligned with the. arcuatemovement ofthe carbonpencil electrode 52 Withinthe chamber, A tinnedclosure B I preferably in' the form ofza disc, .as shown in rigq, is placedin the recess of .each unitjin the mounting. XtureLthentinned ismffacerof the dis-c making rough contatrwith v.6.0'

therecessfsothatair'may be removedirom the interior of the unit. by the pumping. system. When the mounting xture. isloacled with the tinned discs 6I placed .in the recesses of` the unitsy'as .shown-in vFig. .4.; the belljar 33'ffis placedgnthe ring 31 andthe pumpinggsystemstarted to'evlaei-1fate "the .chamberf through .the nozzle .39"to. ajglbv; pressureof one to three inchesxof mercury ab lute; andwhen all the air and moisture-ardt .moved from the 4crystal casing and the'chamber, the nal sealrnay be made if it is desiredto main'- tainthe v.crystal blank. .iria .10W pressure.4 env-iron# ment. YThesealing isperformed by manipulating the shait'.4.2r by theexternal hand knob145ytoybring the carbonpenilrin line witbthe disctl fotone 'or 'tlieuntsfand lowering theearbon pr-:11.9.11l

trode 52 into contact with the disc by pulling the knob 45 downwardly, whereupon the welding circuit is completed throughthe shaft and pencil and the disc on the casing in the mounting unit which latter forms the stationary electrode for the completion or the welding circuit. The heating current melts the solder coating on the discr and the disc is fused over the pin hole opening I9 in the casing to permanently seal the unit.

If it is desired to maintain the crystal blank in a gaseous environment at higher pressure, this may be performed by following the same procedure of evacuation and then'supplying dry air to the chamber through opening r53, the air supply being previously processed so that it does not exceed 18 per cent relative humidity at 25 C. to prevent the entrance of moisture into the sealed casing of the unit. The preferred practice in order to remove moisture and contaminating gases from the casing is to evacuate the chamber to a vacuum pressure of one to three inches of mercury absolute and then inject the dry air into the chamber, these operations being performed alternately several times to insure a relatively moisture-free environment in the sealed casing.

When this procedure is completed the disc 6i is sealed by contact of the carbon pencil to close the opening I9 in each of the crystal units.

The final sealing assembly of this invention provides a controlled atmosphere for the sealing of the crystal unit wherein the sealing is performed manually by the operation of the movable electrode within the chamber and the construction of the movable electrode assembly permits the maintenance of a desired pressure in the chamber without contaminating air leaking into the chamber. This is produced by the yieldable and ilexible sleeve on the standard assembly which permits reciprocal and rotatable movement of the electrode within the chamber by ex- ,1

ternal manipulation so that the unit, after evacuation and lling, may be sealed` while in the puried environment of the chamber and contamination of the filling is prevented.

It is, of course, understood that various modications may be made in the detailed assembly V of the structures and methods herein described without departing from the scope and spirit of the invention as defined in the appended claims.

What is claimed is:

1. In sealing apparatus comprising a chamber having a base portion, a tubular member extending into said base portion, an exhaust connection leading into said chamber, and a mounting i'lxture attached to said b'ase portion adapted to support a casing having an aperture therein to be sealed and an insert covering said aperture sealing means comprising a movable standard extending through said tubular member, a pencil electrode carried by said standard, an expansible and impervious sleeve affixed to said tubular member and standard for reciprocal and rotatable movement of said electrode within said chamber, 7and conductors connected to saidflxture and standard for supplying heating energy for sealing said aperture in said casing by the bonding to said casing about said aperture of said insert covering said aperture.

2. In sealing apparatus comprising a chamber having a base portion, a tubular member extending into said base portion, an exhaust connection leading into said chamber, means for supplying dry air to said chamber, and a mounting block on said base portion adapted to support a plurality of metallic units therein, each of said units having` a pin hole opening covered bya loosely applied tinned disc, sealing means comprising a metallic standard extending through said tubular member, slidable means insulating said standard from said member, an arm projecting from vthe inner end of said standard, a resistive` pencil electrode on said arm directed toward said units in said block, a yieldable sleeve rigidly connected to said tubular member and standard for forming a exible hermetic seal therebetween, a conductor attached to said block, and another conductor attached to said standard exterior to said chamber.

3. In sealing apparatus for an hermetic casing of a crystal unit, comprising a base plate, a bell jar forming a sealed joint with said. base platey and providing a chamber of controlled sealing conditions, a tube joined to said base and extending within said chamber, means for evacuating said chamber to a low pressure, and a mounting fixture. located on said base for supporting the casing of a crystal unit, said casing having a pin hole opening therein and tinned closure superimposed over said opening, sealing means, comprising a reciprocally and rotatably movable standard insulatingly supported within said tube and extending into said chamber and outwardly from said tube for manual operation, a yieldable sleeve member extending from the outer end of said tube to'said standard and sealed to both to prevent entrance of air into said chamber, a resistive pencil electrode projecting downwardly from said standard for engaging said closure whereby fusion and pressure on the closure 'seals the pin hole in said unit, and conductors leading to said standard and fixture for supplying heating current to said closure whereby said closure may be fused to said casing sealingly about said opening.

4. In apparatus having a base, a transparent chamber xed on said base, and means for supporting on edge within said chamber in arcuate array a plurality of piezoelectric crystal units to be sealed, each of said units having therein an aperture overlaid by a tinned insert, the combination of a carbon electrode mounted Within said chamber for arcuate and reciprocable movement, means for supplying electrical potential between said electrode and said base, whereby a heating current supply circuit may be completed through one of said crystal units to be sealed, and means disposed externally of said chamber, extending sealingly thereinto and coupled to said lelectrode for precisely positioning said electrode relative to the insert in any of said units.

JOSEPH F. BARRY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,237,200 Gray Aug. 14, 1917 1,507,166 Garrett Sept. 2, 1924 2,101,156 Payne 'Dec. 7, 1937 2,381,764 McFarland, Jr. Aug. 7, 1945 2,435,747 Larson Feb. 10, 1948 2,459,812 Grifths Jan. 25, 1949 `2,479,024 Pujol y Font Aug. 16, 1949 2,481,042 Tomasek et a1.v-.. Sept. 6, 1949 

